The prevention of primary caries and recurrent caries remains a critical concern in the practice of contemporary dentistry. The demineralization inhibition and remineralization noted with in vitro studies is an encouraging finding, related to the potential for fluoride releasing dental materials to act as a preventive dentistry adjunct for protection of tooth structure surrounding a restoration, as well as the tooth situated adjacently in the dental arch. Continual low-level fluoride release has been sited as effective in preventing tooth demineralization. Since fluoridated dentifrices and fluoride rinses have been shown to effectively inhibit tooth demineralization, one would certainly expect that fluoride-releasing materials would provide a similar or superior benefit. The purpose of this proposal is to effectively evaluate the caries inhibition ability of fluoride releasing dental materials. It has been shown that the mere addition of fluoride to a material does not necessarily mean that caries prevention is provided, in vitro. Primary and secondary caries prevention can reduce the need for future invasive restorative procedures to be implemented. One study phase involves the standardized placement of an experimental fluoride releasing restoration at a control amalgam restoration in primary molars in each of the 40 study participants. These restoration margins will be microscopically examined for demineralization upon natural exfoliation of the teeth. Another study phase involves the placement of a fluoride releasing and amalgam control restoration in 40 study participants, in a highly caries susceptible population, with subsequent clinical evaluation of recurrent caries. The remaining phase will be a six-legged cross-over study to test the demineralization inhibition and remineralization effects of a fluoride containing composite resin, glass ionomer cement and a non- fluoride releasing control restoration to adjacent tooth structure at the interproximal contact area of two posterior teeth. In this study phase the model is dependent on the use of the single section technique which allows before and after measurements of exactly the same tissue. Thus, small changes in lesion characteristics and mineral content may be observed and measured quantitatively. Sections are housed within a crown at the interproximal site, allowing only the natural external portion of the section to be exposed to the oral environment.